CHAETOGNATHA. 
WITH A NOTE ON THOSE COLLECTED BY H.M.S. ‘CHALLENGER’ IN 
SUBANTARCTIC AND ANTARCTIC WATERS. 
By G. Hersert Fowter, B.A., Pa.D., F.LS. 
J 
(1 Chart.) 
I.—THE COLLECTION OF THE ‘DISCOVERY.’ 
THE specimens mentioned below include all those taken south of 40° S., a parallel 
selected to include what appear to be the eritical temperatures which separate a 
temperate and subantarctic plankton from truly Antarctic forms. The material was 
preserved in alcohol, and was mostly in fair condition, but presented the usual 
disadvantages which attend upon the use of this reagent for Chaetognatha. 
Only three species were represented. The tables of formulz,* 
species, serve to show the relation between the more obvious variations which occur in 
given under each 
these southern specimens and those in specimens from other localities. In these tables 
the first column of figures gives the total length in millimetres (including the tail fin) ; 
the second, the length of the tail expressed as a percentage of the total length; the 
third, the number of jaws; the fourth, the number of anterior teeth (or of the only rew 
of teeth in the case of Arohnia); the fifth (when present), the number of posterior 
teeth. 
SAGITTA HEXAPTERA. 
Sayitta hexaptera, D’Orbigny, Voyage dans Amérique méridionale. Tome Y., 3° partie; Mollusques, 
p. 143. (1835-1843.) 
The species was represented by numerous specimens. They agreed with typical 
heraptera in almost every one of such diagnostic features as they had retained, the 
exceptions being that the anterior fin appeared to extend slightly further forward than 
is usually the case (due possibly to imperfect preservation), and that the first (newest) 
jaw hardly showed the usual ridge and bay just below the tip; the extent to which 
* The latest papers on Chaetognatha, summarising the distribution and literature of the group, are: “ Biscayan 
Plankton collected during a cruise of H.M.S ‘ Research,’ 1900, Part III.—The Chaetognatha”’; Transactions of 
the Linnean Society, 2nd Series, Zool., Vol. X., pp. 55-87; and ‘‘ Reports of the ‘Siboga’ Expedition. Mono- 
graph XXI., The Chaetognatha”’ (Leiden, 1906). 
VOL. III. : 
